The present invention relates to a condensing unit for an air conditioning system having a housing with a pair of compartments separated by a common wall and a damper for opening and closing an opening in said common wall to provide for more efficient cooling under ambient temperatures of 60.degree. F. or below.
Vapor-cycle based air conditioning systems are typically limited in their ability to provide cooling to a building when the outdoor air temperature drops below about 60.degree. F. Such system generally comprises a compressor, a condenser coil, expansion means and an evaporator coil operatively interconnected to form the system.
Basically, high-pressure vaporous refrigerant compressed by the compressor is condensed in the condenser. The liquid refrigerant passes through a refrigerant line to the expansion means, where it is metered. The expansion means may be a capillary tube, or a thermal expansion valve. The metered refrigerant passes from the expansion means to the evaporator coil. Air to be cooled is passed over the evaporator coil. Refrigerant gas from the evaporator coil is returned to the compressor through the suction line and the cycle is repeated.
As the outdoor air temperature falls below 60.degree. F., the air circulated over the condenser coil, generally by a fan associated with the condenser coil, causes the refrigerant gas to cool and condense quickly so that the pressure in the refrigerant line to the expansion means falls to unacceptable levels.
Prior solutions to the problem of cooling when the ambient temperature falls below about 60.degree. F. were to reduce the air flow across the condenser coil by slowing the speed of the condenser fan, to cycle the condenser fan on and off or to mechanically block off a portion of the surface of the condenser coil. Stewart's U.S. Pat. No. 3,112,620 shows a refrigeration system with an air-cooled condenser with three separate fans incorporating a control to terminate operation of one fan in response to a predetermined low temperature and thereby increase the condensing pressure. Dapper's U.S. Pat. No. 3,366,167 relates to a refrigeration system with a condensing unit which employs multiple fans, one of which may be turned off to prevent an undesirably low condensing pressure. Neither of these patents suggests the present invention.
Burke's U.S. Pat. No. 2,959,933 discloses a heat pump having an outdoor unit with a damper in a wall separating two compartments, the first compartment containing the compressor and the reversing valve and the second compartment containing the condenser coil and condenser fan. The damper is opened and closed by bimetallic members 32 and 34, which are responsive to the temperature in the two compartments in the outdoor unit. When the resultant temperature of the bimetallic members drops below about 50.degree. F., the damper is closed and the radiant heat generated by the compressor and motor driving the compressor is trapped in the compartment containing the compressor and reversing valve. When the resultant temperature of the bimetallic members exceeds about 50.degree. F., the damper is opened and air may circulate over the compressor, as shown in FIG. 2 of Burke's U.S. Pat. No. 2,959,933, to cool same. The heating cycle of the heat pump of Burke is intended to operate at a higher temperature level to provide a greater heating effect. Burke does not suggest the condensing unit structure of the present invention or its novel mode of operation.
An object of the present invention is to provide an improved condensing unit having a bypass damper in a common wall between two compartments in the condensing unit, for improving performance during cooling operation at outdoor air temperatures below a predetermined level.
Another object of the present invention is to provide an improved condensing unit for a refrigeration system, said condensing unit having two compartments each containing a condenser coil and fan, with a bypass damper in a common wall between the two compartments for permitting air to pass between the two compartments when the outdoor air temperature drops below a predetermined level.
A further object of the present invention is to provide a condensing unit with first- and second-stage compartments each containing a compressor, a condensing coil and a fan, a common wall containing a bypass damper separates the two compartments, and control means for actuating the bypass damper when the outdoor air temperature falls below a predetermined temperature, e.g., 60.degree. F., to permit air to pass from the inoperative second-stage compartment to the operating first-stage compartment to reduce the pressure differential across the condenser coil in the first-stage compartment thereby reducing the airflow over the first-stage coil and increasing the refrigerant pressure in said first-stage coil.
Other objects and advantages of the present invention will be made more apparent hereafter.